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<td ><a href="../qtdoc/index.html">Qt 5.14</a></td><td ><a href="qtgui-index.html">Qt GUI</a></td><td ><a href="qtgui-module.html">C++ Classes</a></td><td >QValidator</td></tr></table><table class="buildversion"><tr>
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<h3><a name="toc">Contents</a></h3>
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<li class="level1"><a href="#public-types">Public Types</a></li>
<li class="level1"><a href="#public-functions">Public Functions</a></li>
<li class="level1"><a href="#signals">Signals</a></li>
<li class="level1"><a href="#details">Detailed Description</a></li>
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<h1 class="title">QValidator Class</h1>
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<p>The QValidator class provides validation of input text. <a href="#details">More...</a></p>
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<tr><td class="memItemLeft rightAlign topAlign"> Header:</td><td class="memItemRight bottomAlign">   <span class="preprocessor">#include &lt;QValidator&gt;</span>
</td></tr><tr><td class="memItemLeft rightAlign topAlign"> qmake:</td><td class="memItemRight bottomAlign"> QT += gui</td></tr><tr><td class="memItemLeft rightAlign topAlign"> Inherits:</td><td class="memItemRight bottomAlign"> <a href="../qtcore/qobject.html">QObject</a></td></tr><tr><td class="memItemLeft rightAlign topAlign"> Inherited By:</td><td class="memItemRight bottomAlign"> <p><a href="qdoublevalidator.html">QDoubleValidator</a>, <a href="qintvalidator.html">QIntValidator</a>, <a href="qregexpvalidator.html">QRegExpValidator</a>, and <a href="qregularexpressionvalidator.html">QRegularExpressionValidator</a></p>
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<li><a href="qvalidator-members.html">List of all members, including inherited members</a></li>
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<a name="public-types"></a>
<h2 id="public-types">Public Types</h2>
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<tr><td class="memItemLeft rightAlign topAlign"> enum </td><td class="memItemRight bottomAlign"><b><a href="qvalidator.html#State-enum">State</a></b> { Invalid, Intermediate, Acceptable }</td></tr>
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<a name="public-functions"></a>
<h2 id="public-functions">Public Functions</h2>
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<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qvalidator.html#QValidator">QValidator</a></b>(QObject *<i>parent</i> = nullptr)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual </td><td class="memItemRight bottomAlign"><b><a href="qvalidator.html#dtor.QValidator">~QValidator</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual void </td><td class="memItemRight bottomAlign"><b><a href="qvalidator.html#fixup">fixup</a></b>(QString &amp;<i>input</i>) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QLocale </td><td class="memItemRight bottomAlign"><b><a href="qvalidator.html#locale">locale</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qvalidator.html#setLocale">setLocale</a></b>(const QLocale &amp;<i>locale</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual QValidator::State </td><td class="memItemRight bottomAlign"><b><a href="qvalidator.html#validate">validate</a></b>(QString &amp;<i>input</i>, int &amp;<i>pos</i>) const = 0</td></tr>
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<a name="signals"></a>
<h2 id="signals">Signals</h2>
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<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qvalidator.html#changed">changed</a></b>()</td></tr>
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<a name="details"></a>
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<div class="descr">
<h2 id="details">Detailed Description</h2>
<p>The class itself is abstract. Two subclasses, <a href="qintvalidator.html">QIntValidator</a> and <a href="qdoublevalidator.html">QDoubleValidator</a>, provide basic numeric-range checking, and <a href="qregexpvalidator.html">QRegExpValidator</a> provides general checking using a custom regular expression.</p>
<p>If the built-in validators aren't sufficient, you can subclass QValidator. The class has two virtual functions: <a href="qvalidator.html#validate">validate</a>() and <a href="qvalidator.html#fixup">fixup</a>().</p>
<p><a href="qvalidator.html#validate">validate</a>() must be implemented by every subclass. It returns <a href="qvalidator.html#State-enum">Invalid</a>, <a href="qvalidator.html#State-enum">Intermediate</a> or <a href="qvalidator.html#State-enum">Acceptable</a> depending on whether its argument is valid (for the subclass's definition of valid).</p>
<p>These three states require some explanation. An <a href="qvalidator.html#State-enum">Invalid</a> string is <i>clearly</i> invalid. <a href="qvalidator.html#State-enum">Intermediate</a> is less obvious: the concept of validity is difficult to apply when the string is incomplete (still being edited). QValidator defines <a href="qvalidator.html#State-enum">Intermediate</a> as the property of a string that is neither clearly invalid nor acceptable as a final result. <a href="qvalidator.html#State-enum">Acceptable</a> means that the string is acceptable as a final result. One might say that any string that is a plausible intermediate state during entry of an <a href="qvalidator.html#State-enum">Acceptable</a> string is <a href="qvalidator.html#State-enum">Intermediate</a>.</p>
<p>Here are some examples:</p>
<ul>
<li>For a line edit that accepts integers from 10 to 1000 inclusive, 42 and 123 are <a href="qvalidator.html#State-enum">Acceptable</a>, the empty string and 5 are <a href="qvalidator.html#State-enum">Intermediate</a>, and &quot;asdf&quot; and 1114 is <a href="qvalidator.html#State-enum">Invalid</a>.</li>
<li>For an editable combobox that accepts URLs, any well-formed URL is <a href="qvalidator.html#State-enum">Acceptable</a>, &quot;http://example.com/,&quot; is <a href="qvalidator.html#State-enum">Intermediate</a> (it might be a cut and paste action that accidentally took in a comma at the end), the empty string is <a href="qvalidator.html#State-enum">Intermediate</a> (the user might select and delete all of the text in preparation for entering a new URL) and &quot;http:///./&quot; is <a href="qvalidator.html#State-enum">Invalid</a>.</li>
<li>For a spin box that accepts lengths, &quot;11cm&quot; and &quot;1in&quot; are <a href="qvalidator.html#State-enum">Acceptable</a>, &quot;11&quot; and the empty string are <a href="qvalidator.html#State-enum">Intermediate</a>, and &quot;http://example.com&quot; and &quot;hour&quot; are <a href="qvalidator.html#State-enum">Invalid</a>.</li>
</ul>
<p><a href="qvalidator.html#fixup">fixup</a>() is provided for validators that can repair some user errors. The default implementation does nothing. <a href="../qtwidgets/qlineedit.html">QLineEdit</a>, for example, will call <a href="qvalidator.html#fixup">fixup</a>() if the user presses Enter (or Return) and the content is not currently valid. This allows the <a href="qvalidator.html#fixup">fixup</a>() function the opportunity of performing some magic to make an <a href="qvalidator.html#State-enum">Invalid</a> string <a href="qvalidator.html#State-enum">Acceptable</a>.</p>
<p>A validator has a locale, set with <a href="qvalidator.html#setLocale">setLocale</a>(). It is typically used to parse localized data. For example, <a href="qintvalidator.html">QIntValidator</a> and <a href="qdoublevalidator.html">QDoubleValidator</a> use it to parse localized representations of integers and doubles.</p>
<p>QValidator is typically used with <a href="../qtwidgets/qlineedit.html">QLineEdit</a>, <a href="../qtwidgets/qspinbox.html">QSpinBox</a> and <a href="../qtwidgets/qcombobox.html">QComboBox</a>.</p>
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<p><b>See also </b><a href="qintvalidator.html">QIntValidator</a>, <a href="qdoublevalidator.html">QDoubleValidator</a>, <a href="qregexpvalidator.html">QRegExpValidator</a>, and <a href="../qtwidgets/qtwidgets-widgets-lineedits-example.html">Line Edits Example</a>.</p>
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<div class="types">
<h2>Member Type Documentation</h2>
<!-- $$$State$$$Invalid$$$Intermediate$$$Acceptable -->
<h3 class="fn" id="State-enum"><a name="State-enum"></a>enum QValidator::<span class="name">State</span></h3>
<p>This enum type defines the states in which a validated string can exist.</p>
<div class="table"><table class="valuelist"><tr valign="top" class="odd"><th class="tblConst">Constant</th><th class="tblval">Value</th><th class="tbldscr">Description</th></tr>
<tr><td class="topAlign"><code>QValidator::Invalid</code></td><td class="topAlign tblval"><code>0</code></td><td class="topAlign">The string is <i>clearly</i> invalid.</td></tr>
<tr><td class="topAlign"><code>QValidator::Intermediate</code></td><td class="topAlign tblval"><code>1</code></td><td class="topAlign">The string is a plausible intermediate value.</td></tr>
<tr><td class="topAlign"><code>QValidator::Acceptable</code></td><td class="topAlign tblval"><code>2</code></td><td class="topAlign">The string is acceptable as a final result; i.e&#x2e; it is valid.</td></tr>
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<h2>Member Function Documentation</h2>
<!-- $$$QValidator[overload1]$$$QValidatorQObject* -->
<h3 class="fn" id="QValidator"><a name="QValidator"></a>QValidator::<span class="name">QValidator</span>(<span class="type"><a href="../qtcore/qobject.html#QObject">QObject</a></span> *<i>parent</i> = nullptr)</h3>
<p>Sets up the validator. The <i>parent</i> parameter is passed on to the <a href="../qtcore/qobject.html">QObject</a> constructor.</p>
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<h3 class="fn" id="changed"><a name="changed"></a><code>[signal] </code><span class="type">void</span> QValidator::<span class="name">changed</span>()</h3>
<p>This signal is emitted when any property that may affect the validity of a string has changed.</p>
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<h3 class="fn" id="dtor.QValidator"><a name="dtor.QValidator"></a><code>[virtual] </code>QValidator::<span class="name">~QValidator</span>()</h3>
<p>Destroys the validator, freeing any storage and other resources used.</p>
<!-- @@@~QValidator -->
<!-- $$$fixup[overload1]$$$fixupQString& -->
<h3 class="fn" id="fixup"><a name="fixup"></a><code>[virtual] </code><span class="type">void</span> QValidator::<span class="name">fixup</span>(<span class="type"><a href="../qtcore/qstring.html">QString</a></span> &amp;<i>input</i>) const</h3>
<p>This function attempts to change <i>input</i> to be valid according to this validator's rules. It need not result in a valid string: callers of this function must re-test afterwards; the default does nothing.</p>
<p>Reimplementations of this function can change <i>input</i> even if they do not produce a valid string. For example, an ISBN validator might want to delete every character except digits and &quot;-&quot;, even if the result is still not a valid ISBN; a surname validator might want to remove whitespace from the start and end of the string, even if the resulting string is not in the list of accepted surnames.</p>
<!-- @@@fixup -->
<!-- $$$locale[overload1]$$$locale -->
<h3 class="fn" id="locale"><a name="locale"></a><span class="type"><a href="../qtcore/qlocale.html">QLocale</a></span> QValidator::<span class="name">locale</span>() const</h3>
<p>Returns the locale for the validator. The locale is by default initialized to the same as QLocale().</p>
<p><b>See also </b><a href="qvalidator.html#setLocale">setLocale</a>() and <a href="../qtcore/qlocale.html#QLocale">QLocale::QLocale</a>().</p>
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<!-- $$$setLocale[overload1]$$$setLocaleconstQLocale& -->
<h3 class="fn" id="setLocale"><a name="setLocale"></a><span class="type">void</span> QValidator::<span class="name">setLocale</span>(const <span class="type"><a href="../qtcore/qlocale.html">QLocale</a></span> &amp;<i>locale</i>)</h3>
<p>Sets the <i>locale</i> that will be used for the validator. Unless setLocale has been called, the validator will use the default locale set with <a href="../qtcore/qlocale.html#setDefault">QLocale::setDefault</a>(). If a default locale has not been set, it is the operating system's locale.</p>
<p><b>See also </b><a href="qvalidator.html#locale">locale</a>() and <a href="../qtcore/qlocale.html#setDefault">QLocale::setDefault</a>().</p>
<!-- @@@setLocale -->
<!-- $$$validate[overload1]$$$validateQString&int& -->
<h3 class="fn" id="validate"><a name="validate"></a><code>[pure virtual] </code><span class="type"><a href="qvalidator.html#State-enum">QValidator::State</a></span> QValidator::<span class="name">validate</span>(<span class="type"><a href="../qtcore/qstring.html">QString</a></span> &amp;<i>input</i>, <span class="type">int</span> &amp;<i>pos</i>) const</h3>
<p>This virtual function returns <a href="qvalidator.html#State-enum">Invalid</a> if <i>input</i> is invalid according to this validator's rules, <a href="qvalidator.html#State-enum">Intermediate</a> if it is likely that a little more editing will make the input acceptable (e.g&#x2e; the user types &quot;4&quot; into a widget which accepts integers between 10 and 99), and <a href="qvalidator.html#State-enum">Acceptable</a> if the input is valid.</p>
<p>The function can change both <i>input</i> and <i>pos</i> (the cursor position) if required.</p>
<!-- @@@validate -->
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